Tuning of a kinematic relationship between members

ABSTRACT

Described herein is a device comprising members in a kinematic relationship. The kinematic relationship is at least partially governed by at least one magnetically induced force that introduces a force threshold that, in effect, provides a threshold to part movement and confers a degree of hysteresis, preventing movement until a sufficiently large energizing force is applied. The effect may be further altered by use of an additional magnetically induced force interaction with at least one further member to urge or slow movement once started and/or to prevent movement once a new position is reached.

RELATED APPLICATIONS

This application derives priority from New Zealand patent applicationnumber 627630 incorporated herein by reference.

BACKGROUND Technical Field

Described herein is a device comprising members in a kinematicrelationship, the kinematic relationship at least partially governed byat least one magnetically induced force that introduces a forcethreshold that, in effect, may provide a threshold and confer a degreeof hysteresis, preventing movement until a sufficiently large energizingforce is applied. The effect may be further altered by use of anadditional magnetically induced force interaction with at least onefurther member to urge or slow movement once started and/or to preventmovement once a new position is reached.

Description of the Related Art

Eddy current formation may be used in a variety of ways to adjust thespeed of rotation of a member. Various apparatus exist, for example inabseiling, to control the descent of a climber or for example, inpersonal protective equipment scenarios to prevent an injury causingfall. Other applications that use eddy current generation are incontrolling pay-out of line in trains, cable cars, zip line devices androller coasters.

One art device is published as US2012/0055740. This device utilizes arotor assembly with arms that move relative to the rotor. The armsthemselves may be conductive or magnetic or may have conductive ormagnetic members attached thereto. When a rotational force is applied tothe rotor, the arms move outwards from a central axis via centrifugalforce and into a magnetic (or conductive) field. As the arms movethrough the field, eddy currents are generated, the strength of which isdependent on the speed of rotation. As the speed of rotation reduces,the arms are drawn back towards the axis of rotation via springs and/ora reduced centrifugal force acting on the arms. This device is widelyused and provides an excellent means of changing the relative speed ofparts.

One aspect of the above apparatus is that there is minimal hysteresisbetween activation of the braking effect and non-activation. This canresult is rapid on-off switching of the braking effect termed ‘chatter’.Chatter in some applications is particularly undesirable. For example,in fall safety applications, an auto belay may be attached to a harnessworn by a person in danger of a fall. If a fall occurs, the devicebrakes and/or stops a fall thereby preventing injury or loss of life.Chatter becomes a hindrance in fall safety use. For example, unwantedactivation of the brake effect may occur when the person moves suddenly(but not a fall). False activation may result in tiring the person; theperson may loose balance and fall; or false activation simply becomes ageneral nuisance factor. In worst cases, chatter may discourage use ofthe fall safety device and lead to serious injury or loss of life.

Urging or slowing movement of the arms once started in the above devicevia a further input may also be useful depending on the end applicationof the device.

As may be appreciated, providing a means of both slowing and/or fullystopping relative movement between parts in a means that may be tuned toavoid inadvertent braking and induce a tunable degree of hysteresis maybe useful or at least it provides the public with a choice.

Further aspects and advantages of the device will become apparent fromthe ensuing description that is given by way of example only.

BRIEF SUMMARY

Described herein is a device comprising members in a kinematicrelationship, the kinematic relationship at least partially governed byat least one magnetically induced force that introduces a forcethreshold that, in effect, may provide a threshold and confer a degreeof hysteresis, preventing movement until a sufficiently large energizingforce is applied. The effect may be further altered by use of anadditional magnetically induced force interaction with at least onefurther member to urge or slow movement once started and/or to preventmovement once a new position is reached.

In a first aspect, there is provided a device comprising:

at least one first member or a part thereof and at least one secondmember or a part thereof, the first and second members beingapproximately adjacent to each other and in a constrained kinematicrelationship relative to each other;

at least one magnetically attracted relationship between the at leastone first and second members forming a magnetically induced forcebetween the members or a part thereof; and

wherein the magnetically induced force provides a force thresholdpreventing movement between the members and, when this threshold isexceeded by application of an energizing force, relative motion occursvia a dynamic system according to the kinematic relationship between theat least one first member and at least one second member.

In a second aspect, there is provided a device comprising:

at least one first member or a part thereof coupled to a second memberand at least one third member or a part thereof, the first and thirdmembers being approximately adjacent to each other and in a constrainedkinematic relationship relative to each other;

at least one magnetically attracted relationship between the at leastone first and third members forming a magnetically induced force betweenthe members or a part thereof; and

wherein the magnetically induced force provides a complementary forceovercoming a force threshold resisting movement between at least thefirst and third members such that, when this threshold is exceeded byapplication of an energizing force:

(a) relative motion occurs via a dynamic system according to thekinematic relationship between the at least one first and third member;and

(b) the induced force accelerates the motion of the first memberrelative to the third; and

(c) the induced force provides a holding force resisting reversal of therelative motion.

In a third aspect, there is provided a brake comprising:

a device substantially as described above; and

wherein the at least one first member or a part thereof is at leastpartially electrically conductive and in a further kinematicrelationship with an independent magnetic field such that:

(a) prior to a sufficient energizing force, the at least one firstmember and at least one second member remain magnetically coupled and afirst no or low induced eddy current brake effect occurs; and

(b) on application of an energizing force sufficient to overcome themagnetically induced force, the at least one first member moves into themagnetic field thereby inducing an eddy current brake effect on movementof the at least one first member or a part thereof relative to themagnetic field.

In a fourth aspect, there is provided a line dispensing deviceincorporating at least one device substantially as described above.

In a fifth aspect, there is provided a passenger seat restraintincorporating at least one device substantially as described above.

In a sixth aspect, there is provided a transmission drive incorporatingat least one device to engage a rotational drive substantially asdescribed above.

In a seventh aspect, there is provided a linear guided lifelineincorporating at least one device substantially as described above.

Numerous other applications of the device may also be possible asfurther outlined in the description below.

One advantage of the above device includes the ability to control whenmovement prescribed by the kinematic relationship occurs. In addition, afurther advantage of the device is to also influence the kinematicrelationship once movement commences. The magnitude of the inertiaeffect may be tuned between extremes of a high resistance to movementthrough to a low resistance to movement. In addition, through use of anadditional magnetic member, the threshold and rate of movement via thekinematic relationship may also be influenced greater or less. Tuning inthis way may have the effect of avoiding on/off chatter and confer adegree of hysteresis in the device action. Through a third member,deactivation may also be tuned so as to avoid accidental disengagementfor example from a latch. Another, further advantage of the above deviceis the wide range of ability to control and vary movement via thekinematic relationship meaning the device is able to be used in a rangeof different ways and applications and may minimize the likelihood offalse activations.

BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS

Further aspects of the device will become apparent from the followingdescription that is given by way of example only and with reference tothe accompanying drawings in which:

FIG. 1 illustrates a side view of one embodiment of a device in amagnetically attracted relationship;

FIG. 2 illustrates a graph showing the relationship between themagnetically attracted force and movement of the pawl or first member;

FIG. 3 illustrates a side view of an alternate embodiment incorporatinga rotating second member and a first member with two magneticrelationships;

FIG. 4 illustrates a side view of an alternate embodiment incorporatinga rotating second member and a first member with two magneticrelationships;

FIG. 5 illustrates a graph showing the modified relationship that occurswith the arrangement used in FIGS. 3 and 4;

FIG. 6 illustrates a side view of an alternate embodiment incorporatinga rod shaped first member;

FIG. 7 illustrates a side view of an alternate embodiment incorporatinga rotating third member and a fixed second member and relative movingfirst member;

FIG. 8 illustrates a side view of an alternate embodiment to FIG. 7incorporating a rod shaped first member;

FIG. 9 illustrates a side view of an alternate embodiment incorporatinga sliding second member and a pivoting first member pawl;

FIG. 10 illustrates a side view of an alternative embodiment to FIG. 9incorporating a rod shaped second member;

FIG. 11 illustrates a side view of a further alternative with a fixedsecond member and moving third member;

FIG. 12 illustrates a side view of a further alternative to FIG. 11using a rod shaped first member; and

FIG. 13 illustrates a perspective view of a further alternative shapeddevice.

DETAILED DESCRIPTION

As noted above, described herein is a device comprising members in akinematic relationship, the kinematic relationship at least partiallygoverned by at least one magnetically induced force that introduces aforce threshold that, in effect, may provide a threshold and confer adegree of hysteresis, preventing movement until a sufficiently largeenergizing force is applied. The effect may be further altered by use ofan additional magnetically induced force interaction with at least onefurther member to urge or slow movement once started and/or to preventmovement once a new position is reached.

For the purposes of this specification, the term ‘about’ or‘approximately’ and grammatical variations thereof mean a quantity,level, degree, value, number, frequency, percentage, dimension, size,amount, weight or length that varies by as much as 30, 25, 20, 15, 10,9, 8, 7, 6, 5, 4, 3, 2, or 1% to a reference quantity, level, degree,value, number, frequency, percentage, dimension, size, amount, weight orlength.

The term ‘substantially’ or grammatical variations thereof refers to atleast about 50%, for example 75%, 85%, 95% or 98%.

The term ‘comprise’ and grammatical variations thereof shall have aninclusive meaning—i.e., that it will be taken to mean an inclusion ofnot only the listed components it directly references, but also othernon-specified components or elements.

The term ‘energizing force’ and grammatical variations thereof refers toa force that acts to impose a rate of movement on an object.

The term ‘dynamic’ and grammatical variations thereof in the context ofdevice or device part movement refers to forces induced by mechanicalmeans and for the purposes of this specification, excludes forces thatmight arise from liquid fluid movement or pressure.

In a first aspect, there is provided a device comprising:

at least one first member or a part thereof and at least one secondmember or a part thereof, the first and second members beingapproximately adjacent to each other and in a constrained kinematicrelationship relative to each other;

at least one magnetically attracted relationship between the at leastone first and second members forming a magnetically induced forcebetween the members or a part thereof; and

wherein the magnetically induced force provides a force thresholdpreventing movement between the members and, when this threshold isexceeded by application of an energizing force, relative motion occursvia a dynamic system according to the kinematic relationship between theat least one first member and at least one second member.

Relative motion in the above aspect between the at least one firstmember and the at least one second member may initially be prevented bythe device above and wherein the device further comprises:

at least one further magnetically attracted relationship between a thirdmember and the at least one first member and/or at least one secondmember forming a second magnetically induced force between the at leastone third member or a part thereof and the first and/or second member ormembers or a part thereof; and

wherein the second magnetically induced force provides a complementaryforce overcoming a force threshold resisting movement between themembers such that, when this threshold is exceeded by application of anenergizing force:

relative motion occurs via the kinematic relationship between the atleast one first and second member; and

(a) the second induced force accelerates the motion of the first and/orsecond member relative to the third member or members; and

(b) the second induced force provides a holding force resisting reversalof the relative motion.

The first and second members may be coupled together. Coupling may bedirect or indirect, for example via a spring or other member.

In a second aspect, there is provided a device comprising:

at least one first member or a part thereof coupled to a second memberand at least one third member or a part thereof, the first and thirdmembers being approximately adjacent to each other and in a constrainedkinematic relationship relative to each other;

at least one magnetically attracted relationship between the at leastone first and third members forming a magnetically induced force betweenthe members or a part thereof; and

wherein the magnetically induced force provides a complementary forceovercoming a force threshold resisting movement between at least thefirst and third members such that, when this threshold is exceeded byapplication of an energizing force:

(a) relative motion occurs via a dynamic system according to thekinematic relationship between the at least one first and third member;and

(b) the induced force accelerates the motion of the first memberrelative to the third; and

(c) the induced force provides a holding force resisting reversal of therelative motion.

The complementary force noted above may act with inertia forces on thefirst member or members to overcome the initial magnetically attractedrelationship thereby altering the movement characteristics of thedevice.

The magnetically induced force described in the above aspects may bebetween at least one ferromagnetic element and/or region on and/orwithin the at least one first member and at least one magnetic elementand/or region on and/or within the at least one second member.

The magnetically induced force may be between at least one ferromagneticelement and/or region on and/or within the at least one second memberand at least one magnetic element and/or region on and/or within the atleast one first member.

The magnetically induced force may be between at least one magneticelement and/or region on and/or within the at least one first member ofa first polarity and at least one magnetic element and/or region onand/or within the at least one second member of a second polarityopposite to that of the first polarity.

As should be appreciated from the above examples, the way themagnetically induced force occurs may be varied, not limited tocombinations of adjacent magnets or order or positioning offerromagnetic and magnetic elements and respective members.Additionally, it should be appreciated, that the magnetically attractedmaterial need not be limited to ferromagnetic material and may extend toparamagnetic materials—as such, use of the term ‘ferromagnetic’ orgrammatical variations thereof herein, also encompasses othermagnetically attracted materials including, but not limited to,paramagnetic materials.

Movement of the first member once the magnetically induced force isovercome may be direct—that is the first member moves directly due tothe energizing force. The first member may instead move indirectly or byproxy at least in part due to the energizing force causing at least oneadditional mechanical part or force dynamic to move or interact with thefirst member and thereby subsequently causing motion of the firstmember. Indirect means may be a dynamic force transfer via another partsuch as a coupling or gear or a centrifugal force being imposed on thefirst member by direct force on another part. Indirect or proxy forcetransfer may have the advantage of being able to amplify the energizingforce.

Static or dynamic positional and/or strength adjustment of the point ofaction of the magnetically induced force may also be completed by:

adjusting the position of a magnetic element or conductive region on theat least one first member or part thereof as the first member or secondmember moves; and/or,

(a) adjusting the position of a magnetic element or conductive region onthe at least one second member as the at least one first member orsecond member moves.

By way of example, the first member may comprise a slot and a portion ofthe first member comprising the magnetic element or conductive regionmoves within the slot as the first member as a whole moves onapplication of the energizing force. This additional means of adjustingmovement may be useful to further alter the force dynamics and hence theway the parts interact and hence further change the force threshold.

Relative movement between the first member and additional member ormembers may be frictionless. Magnetic forces such as the induced forcenoted above and any subsequent forces acting on the first member mayavoid friction contact. This may be useful to minimize mechanicalwearing on the parts.

In one embodiment, movement between the parts is predominantly governedby dynamic forces. The device may be free of liquid fluid with allmovement between the parts due to dynamic forces. Alternatively, thedevice may have some liquid fluid present but the predominant energizingforce on the device members is dynamic force. Liquid based systemsutilizing magnetics to alter kinematic relationships exist but thesedevices differ to that described herein in that that are oftenbi-stable—that is, the parts are only stable in two positions. Inaddition, movement predominantly or wholly relies on a force or pressurebuild up from the liquid fluid as opposed to dynamic forces. Liquidbased devices also have inherent difficulties associated with sealingthe liquid and more regular maintenance being required to ensurereliable running.

The kinematic relationship may be rotational or linear.

With respect to a rotational relationship:

-   -   The at least one first member may be a pawl or arm shaped member        or members that may be mechanically linked to a second member        that may be a rotor that rotates on application of the        energizing force; and/or    -   The at least one first member may be positioned adjacent to the        rotor and part of the at least one first member may move outside        the region bound by the rotor on application of a sufficiently        large energizing force to overcome the magnetically induced        force; and/or    -   The at least one first member may be pivotally attached to the        rotor about a pivot axis offset from the rotor axis.

With respect to a linear relationship:

-   -   The at least one first member may be a pawl or arm shaped member        or members that may be mechanically linked to a second member        that may be a carriage that translates on application of the        energizing force; and/or    -   The at least one first member may be linearly attached to the        carriage about a pivot axis offset from the direction of motion        of the carriage.

The at least one first member or a part thereof may be positioned toengage with at least one latching member upon movement of the at leastone first member and at least one second member when the energizingforce is applied. Engagement of the at least one first member and atleast one latching member may result in no relative motion between theat least one second member and the at least one latching member.

The third member may be at least one latching member positioned toengage with the at least one first member upon movement of the at leastone first member when the energizing force is applied.

The at least one first member or a part thereof may be electricallyconductive and, relative movement after the threshold is overcome causesthe at least one first member to move into a magnetic field wherein aneddy current induced drag effect occurs on movement of the at least onefirst member.

The device may include a magnetic field that interacts with movement ofthe first member thereby inducing an eddy current drag force on thefirst member causing linear and/or rotational translation of the atleast one first member about a line or point, inclined or offsetrespectively from the line of action of the eddy current induced dragforce.

The at least one first member may move at least partially orthogonallyto the direction of movement of the second member as defined by thekinematic relationship and/or pivotally relative to the magnetic fieldon application of the energizing force.

The kinematic relationship may be constrained by use of an aperture inthe at least one first member defining the range of movement and a stopdefines one or more distal points of the aperture. The magneticallyattracted relationship may exist about each distal point of theaperture.

The magnetic field may be stationary or moving at a different relativespeed to the at least one first member.

The rate at which the at least one first and second members moverelative to each other may be further tuned by varying at least one of:

(a) the magnetic surface area;

(b) the magnetic force strength;

(c) the proximity of the at least one magnetic element and/or region toadjacent at least one magnetic or ferromagnetic element and/or regions;

(d) the geometry and/or magnetic properties of the at least one magneticelement;

(e) the ferromagnetic content of the at least one ferromagnetic elementand/or regions;

(f) the magnetic susceptibility of the ferromagnetic material

As should be appreciated from the above, the members may take variousshapes or weights, factors that influence the activation and/or rate ofmotion of the member or members once movement is initiated. The magneticinteraction may for example be continuous across a first member lengthor spaced apart or of varying dimensions to thereby adjust the fluxoccurring. The magnetically interacting portion of the first or othermembers may be the whole member or only a portion thereof. Where only aportion of the member magnetically interacts, the location of theinteracting portion either on the exterior, interior or part of themember, can be altered.

In a third aspect, there is provided a brake comprising:

a device substantially as described above; and

wherein the at least one first member or a part thereof is at leastpartially electrically conductive and in a further kinematicrelationship with an independent magnetic field such that,

(a) prior to a sufficient energizing force, the at least one firstmember and at least one second member remain magnetically coupled and afirst no or low induced eddy current brake effect occurs; and,

(b) on application of an energizing force sufficient to overcome themagnetically induced force, the at least one first member moves into themagnetic field thereby inducing an eddy current brake effect on movementof the at least one first member or a part thereof relative to themagnetic field.

In a fourth aspect, there is provided a line dispensing deviceincorporating at least one device substantially as described above. Linedispensing devices such as auto belay devices are widely used to preventfalls in both recreational and industrial applications. In some cases,magnetically attracted relationships may be useful to tune the autobelay device characteristics.

In a fifth aspect, there is provided a passenger seat restraintincorporating webbing for extending and retracting, the webbingoperatively coupled to at least one device substantially as describedabove. One example of a passenger seat restraint may be a seat belt usedin a vehicle such as a car. Seat belts are a critical safety feature andthe above described device may provide a useful alternative to existingdesigns particularly given the ability to tune the response in the widevariety of ways noted.

In a sixth aspect, there is provided a transmission drive incorporatingat least one device to engage a rotational drive substantially asdescribed above.

In a seventh aspect, there is provided a linear guided lifelineincorporating at least one device substantially as described above.

The above examples should not be seen as limiting since the devicesdescribed may be used for a wide variety of other applications,non-limiting examples including speed control of:

-   -   a rotor in a rotary turbine;    -   exercise equipment, e.g., rowing machines, epicyclic trainers;    -   roller-coasters and other amusement rides;    -   Elevator and escalator systems;    -   evacuation descenders and fire escape devices;    -   conveyer systems:    -   rotary drives in factory production facilities;    -   materials handling devices such as conveyer belts or a braking        device in a chute;    -   dynamic display signage to control the rate of change of        rotating signs;    -   roadside safety systems, e.g., the eddy current brake may be        connected in a system to provide crash attenuation though the        dissipation of energy via the brake;    -   seat belts in vehicles;    -   braking mechanisms for trolleys and carriages.

As noted above, one advantage of the above device includes the abilityto control when movement prescribed by the kinematic relationshipoccurs. In addition, a further advantage of the device is to alsoinfluence the kinematic relationship once movement commences. Themagnitude of the inertia effect may be tuned between extremes of a highresistance to movement through to a low resistance to movement. Inaddition, through use of an additional magnetic member, the thresholdand rate of movement via the kinematic relationship may also beinfluenced greater or less. Tuning in this way may have the effect ofavoiding on/off chatter and confer a degree of hysteresis in the deviceaction. Through a third member, deactivation may also be tuned so as toavoid accidental disengagement for example from a latch. Another,further advantage of the above device is the wide range of ability tocontrol and vary movement via the kinematic relationship meaning thedevice is able to be used in a range of different ways and applicationsand minimize the likelihood of false activations.

The embodiments described above may also be said broadly to consist inthe parts, elements and features referred to or indicated in thespecification of the application, individually or collectively, and anyor all combinations of any two or more said parts, elements or features,and where specific integers are mentioned herein which have knownequivalents in the art to which the embodiments relates, such knownequivalents are deemed to be incorporated herein as of individually setforth,

Where specific integers are mentioned herein which have knownequivalents in the art to which this invention relates, such knownequivalents are deemed to be incorporated herein as if individually setforth.

WORKING EXAMPLES

The above described device is now described by reference to specificexamples.

For ease of description in the examples, only a single first member istypically shown although it should be appreciated that multiple firstmembers may be used.

A magnetic field through which the first member(s) move and third orlatching member are generally shown for prolixity as continuous regions.The magnetic field, (if present at all) may for example be a series ofdiscrete magnets or even just one magnet. Similarly, the third member(if present) may take on various shapes or surface contours, with only alimited number of examples shown for clarity.

While certain movement, for example of the first member(s) may be shownin an example, it should be appreciated that the magnetic field ifpresent, the second member and/or the third member(s) may also move oreven the first member remain fixed while the other member(s) move.

Example 1

As illustrated by the schematic of FIG. 1, the device 1 in theembodiment shown comprises a first member 2 moving relative to a secondmember 5, in this example shown as being a rotor that rotates aboutrotor axis 6 in direction A. A third member 4 is also shown.

The first member 2 as shown is attached to the second member 5 and akinematic relationship exists between the parts constrained by the firstmember pivot axis 7, the location of the third member 4 and the speed ofrotation of the second member 5.

A magnetically induced force is in place between the first member 2 andthe second member 5 via a magnet or magnets 8, in the Figure shown asbeing a block shape and linked to the second member 5. The first member2 includes a portion 9 or as a whole is magnetically attracted to themagnet 8. The magnetically induced force prevents relative movementbetween the first member 2 and second member 5 until a threshold force Fis exceeded by an energizing force E. In the embodiment of FIG. 1, theenergizing force is created by rotation of the second member 5sufficiently fast that due to centrifugal and inertial action, thethreshold force F is overcome and the first member 2 rotates about thepivot axis 7.

FIG. 2 illustrates this action comparing movement of the first member 2(termed a pawl in FIG. 2) versus the force F applied. No or minimalmovement occurs until the energizing force is reached (marked as Ftrigger in FIG. 2) after which point the magnetically induced forcedissipates quickly as the first member 2 moves away from the secondmember 5. As should be appreciated, introducing the input of a thresholdforce slows activation of the first member 2 and hence adjusts thetiming of any subsequent event brought on by movement of the firstmember 2.

The kinematic relationship between the members 2, 5 may be altered invarious ways, one example being to alter the threshold force by varyingthe conductivity of the first member 2 or by varying the magnet 8dimensions and/or placement (e.g., recessed into the second member 5).

Example 2

FIG. 3 illustrates an addition to the device of Example 1. In thisexample, a third member 4 is added, the third member 4 applying amagnetically induced force on the first member 2 thereby furtherchanging the kinematic relationship between the various members 2, 4, 5.In the embodiment shown, a magnet is placed on the third member 4 thatattracts a portion 9 or all of the first member 2. The induced force tothe third member 4 is not sufficiently strong enough to overcome theinduced force between the first member 2 and second member 5 untilsufficient energizing force is applied (e.g., via rotation of the secondmember 5 about axis 6) to overcome the threshold force. When movement ofthe first member 2 starts to occur, the magnet on the third member 4 maythen urge motion of the first member 2 to the third member 4. The magnet10 on the third member 4 may also provide sufficient force to hold thefirst member 2 against the third member 4. A magnetic field 3 may lieadjacent to the first member 2 and may also apply a braking force onmovement of the first member 2 due to magnetically induced eddy currenteffects.

FIG. 4 illustrates an alternative embodiment that may be used to achievethe above interactions. In this case, the first member 2 is shaped tohave a jaw and a stop connected to a second member 5 lies within the jawregion. The first member 2 is in a kinematic relationship with thesecond member 5 so that when the second member 5 rotates, a centrifugalforce occurs on the first member 2 causing it to move outwards relativeto the second member 5 axis of rotation about the first member pivotaxis 7. The jaws of the first member 2 act to define maximal movement.The stop may be a magnet 8 that is magnetically attracted to a side 9 orall of the first member 2 jaws. This embodiment has a similar effect tothat of FIG. 3 albeit that the first member jaws act as separate pointswhere magnetically induced forces act.

FIG. 5 shows a graph of how the forces in either the embodiment of FIG.3 or FIG. 4 would interact relative to the first member 2 as it moves.The magnetically induced force is high at either extreme of movement ofthe first member 2 and low midway. The magnetically induced force isovercome once the energizing force overcomes a threshold indicated bythe words ‘trigger’ and ‘hold’ on the graph.

Example 3

FIG. 6 illustrates a further embodiment where the first member 2 takesthe form of a rod, the rod 2 translating into or out of an aperture (notshown) in the second member 5 along line of translation marked XX.Rotation of the second member 5 about axis A induces an energizing forcethat, once the magnetically induced force between magnet 8 and thesecond member 5 is overcome, causes translation of the rod 2 out of theaperture and one end of the rod 2 may interact with a third member 4 viaa further magnet (not shown). This example illustrates how the firstmember 2 may take on different shapes and forms and movement of thefirst member 2 may be via an axis of rotation as in earlier Examples ortranslation as in this example.

Example 4

FIG. 7 illustrates a further embodiment of the latch device 1. In thisembodiment, the second member 5 and first member 2 lie on the outsidecircumference of a rotating magnetic field 3 and the third member 4, theaxis of rotation being item 6 and the direction of movement being in aclockwise direction. The first member 2, on application of an energizingforce, overcomes the magnetically induced force between the magnet 8linked to the second member 5 and the first member 2, and then movesabout a rotation axis 7 with at least part of the first member 2 movinginto the magnetic field 3. In the embodiment shown, an eddy current dragforce (not shown) is induced urging rotation of the first member 2 untilthe first member 2 engages with the third member 4 halting relativerotation of the third member 4 and magnetic field 3. Note that the thirdmember 4 need not be present or instead, the third member 4 may simplyact as a stop to further rotation of the first member 2 but not latch.

Example 5

As illustrated in FIG. 8, the same principle shown in FIG. 7 can beapplied using the rod shaped first member 2 first discussed in Example 3above. In this example, the second member 5 and first member rod 2 arefixed in position on a part of the circumference of the device 1 and themagnetic field 3 and third member 4 rotate about axis 6 in direction A.It should be noted that the first member rod 2 is offset in a directioninclined relative to the direction of rotation so as to allowtranslational movement of the rod 2 out of (and back into) the secondmember 5 under the influence of inertial effects.

Example 6

Referring to FIG. 9, an alternative embodiment is shown where linearmotion is used as opposed to rotational motion illustrated in the aboveExamples.

The second member 5 moves along a plane in direction YY. A first member2 in this case shown as a pawl with one end attached to a pivot axis 7is fastened to the second member 5. A magnet 8 is located on the secondmember 5 that creates a magnetically induced force with the first member2. When the second member 5 moves in a linear direction YY, the firstmember 2 overcomes a threshold force and then moves into the magneticfield 3 and is urged via eddy current drag forces and inertial forces torotate about the axis 7 until the first member 2 or a part there ofstrikes and engages the third member 4.

Example 7

FIG. 10 shows a similar embodiment to that of Example 6, this time usinga rod as the first member 2 that translates via line XX instead ofrotating about an axis. The rod 2 interacts with a magnet 8 located onthe second member 5. As the second member 5 moves in a linear directionYY, the first member rod 2 is drawn out of the second member 5 due tothe eddy current induced drag force and inertial force due to movementof the rod 2 in the magnetic field 3.

Example 8

FIG. 11 shows an embodiment similar to that described in Example 6however, in FIG. 11, the magnetic field 3 and third member 4 move inlinear direction YY and the pawl shaped first member 2 and second member5 remain stationary relative to the direction YY movement. The movementof the magnetic field 3 overcomes the magnetically induced force betweenthe magnet 8 and a side or all of the first member 2 thereby urgingmovement of the conductive first member 2 about axis 7 until the firstmember 2 engages the third member 4 at which point relative movement ishalted.

Example 9

FIG. 12 shows the embodiment of Example 8 however this time using a rodshaped first member 2 described in earlier Examples. As should beappreciated, the first member 2 shape can also be altered in thisscenario of a fixed second member 5 and moving magnetic field 3 andlatch member 4.

Example 10

FIG. 13 illustrates a yet further variation of the device 1. In thisexample, the first member 2 is formed as a tube. The first member tube 2may move rotationally about direction B and translate in a lineardirection A along the axis of rotation. The first member tube 2 may bemoved via translation direction A, into a second member that may be amagnet or magnetized cylinder 3. Translational movement may berestrained by use of a magnet 8 linked to the axis of rotation. Themagnet 8 forms a magnetically induced force between the magnet 8 andfirst member 2 until a sufficient threshold force is reached by anenergizing force. When the threshold is reached, the first member 2translates into the second member 3. Relative variation in movementbetween the first member 2 and second member 3 induces an eddy currentdrag that slows rotation of the tube 2 relative to the magnetizedcylinder 3. Optionally, a pawl 20 may engage a third member, in thiscase a latch 4, in this example, the latch 4 may be a mating indentationinside the second member 3 that the pawl 20 interlocks with. A furthermagnet (not shown) may be incorporated on or in the third member 4 tocreate a magnetically induced force between the parts. Translationalmovement of the tube 2 may be urged via a driving mechanism such as athreaded shaft 30.

Aspects of the device have been described by way of example only and itshould be appreciated that modifications and additions may be madethereto without departing from the scope of the claims herein.

These and other changes can be made to the embodiments in light of theabove-detailed description. In general, in the following claims, theterms used should not be construed to limit the claims to the specificembodiments disclosed in the specification and the claims, but should beconstrued to include all possible embodiments along with the full scopeof equivalents to which such claims are entitled. Accordingly, theclaims are not limited by the disclosure.

The invention claimed is:
 1. A brake device comprising: at least onefirst member being a pawl or arm mechanically linked to a second member,the second member being a rotating rotor, and at least one third member,the at least one third member interacting with the at least one firstmember based on relative movement between the at least one first and atleast one third members inducing an eddy current brake effect betweenthe at least one first and third members; at least one magneticallyattracted relationship between the at least one first and second membersthat introduces a force threshold that confers a degree of hysteresispreventing movement between the first and second members up to a forcethreshold and, when this force threshold is exceeded by application ofan energizing force of sufficient magnitude to the second member, themagnetically attracted relationship between the first and second membersis overcome and the at least one first member then moves relative to thesecond member; and as the at least one first member moves relative tothe second member, the at least one first member interacts with thethird member to induce an eddy current brake effect between the at leastone first and third members in turn braking relative movement betweenthe third member and second member via the at least one first member. 2.The brake device as claimed in claim 1 wherein the magneticallyattracted relationship is between at least one ferromagnetic elementand/or region on and/or within the at least one first member and atleast one magnetic element and/or region on and/or within the secondmember.
 3. The brake device as claimed in claim 1 wherein themagnetically attracted relationship is between at least oneferromagnetic element and/or region on and/or within the second memberand at least one magnetic element and/or region on and/or within the atleast one first member.
 4. The brake device as claimed in claim 1wherein the magnetically induced force is between at least one magneticelement and/or region on and/or within the at least one first member ofa first polarity and at least one magnetic element and/or region onand/or within the second member of a second polarity opposite to that ofthe first polarity.
 5. The brake device as claimed in claim 1 whereinthe at least one first member moves directly due to the energizingforce.
 6. The brake device as claimed in claim 1 wherein the at leastone first member moves indirectly at least in part due to the energizingforce imposed on the second member causing at least one additionalmechanical part or force dynamic to move or interact with the at leastone first member and thereby subsequently causing motion of the at leastone first member.
 7. The brake device as claimed in claim 1 whereinrelative movement between the at least one first member and at least onethird member is frictionless.
 8. The brake device as claimed in claim 1wherein the at least one first member is linked to the rotor at aposition adjacent to the rotor and, when the magnetically attractedrelationship is overcome, at least part of the at least one first membermoves outside the region bound by the rotor.
 9. The brake device asclaimed in claim 8 wherein the at least one first member is pivotallyattached to the rotor about a pivot axis offset from the rotor axis. 10.The brake device as claimed in claim 1 wherein once the magneticallyattracted relationship is overcome, the at least one first member movesrelative to the second member until the at least one first memberengages with at least one latching member on or separate to the at leastone third member and, when engagement occurs relative motion isprevented between the second member and at least one latching member viathe at least one first member.
 11. The brake device as claimed in claim1 wherein the at least one first member or a part thereof iselectrically conductive and the at least one third member comprises atleast one magnet generating a magnetic field.
 12. The brake device asclaimed in claim 1 wherein the at least one first member or a partthereof is at least one magnet generating a magnetic field and the atleast one third member is itself in part or in whole electricallyconductive.
 13. The brake device as claimed in claim 1 wherein the atleast one third member is stationary relative to the at least one firstmember.
 14. The brake device as claimed in claim 1 wherein the brakedevice is free of liquid.
 15. A line dispensing device incorporating atleast one brake device as claimed in claim
 1. 16. A passenger seatrestraint incorporating at least one brake device as claimed in claim 1.17. A transmission drive incorporating at least one brake device toengage a rotational drive as claimed in claim
 1. 18. A linear guidedlifeline incorporating at least one brake device as claimed in claim 1.19. A brake device comprising: at least one first member being a pawl orarm mechanically linked to a second member, the second member being alinear translating carriage, and at least one third member, the at leastone third member interacting with the at least one first member based onrelative movement between the at least one first and at least one thirdmembers inducing an eddy current brake effect between the first andthird members; at least one magnetically attracted relationship betweenthe at least one first and second members that introduces a forcethreshold that confers a degree of hysteresis preventing movementbetween the at least one first and second members up to a forcethreshold and, when this force threshold is exceeded by application ofan energizing force of sufficient magnitude to the second member, themagnetically attracted relationship between the first and second membersis overcome and the at least one first member then moves relative to thesecond member; and as the at least one first member moves relative tothe second member, the at least one first member interacts with thethird member to induce an eddy current brake effect between the firstand third members in turn braking relative movement between the thirdmember and second member via the at least one first member.
 20. Thebrake device as claimed in claim 19 wherein the carriage linearlytranslates on application of the energizing force and, when themagnetically attracted relationship is overcome, at least part of the atleast one first member moves outside the region bound by the carriage.21. The brake device as claimed in claim 20 wherein the at least onefirst member is pivotally attached to the carriage.